1. Field of the Invention
Embodiments of the present invention generally relate to running a tubular into a wellbore. More specifically, embodiments of the present invention relate to using a circulating tool for running casing into a wellbore.
2. Description of the Related Art
To obtain hydrocarbons from an earth formation, a wellbore is typically drilled to a first depth using a drill string having a drill bit attached to its lower end. The drill string is then removed, and thereafter a first casing is lowered into the wellbore to line the wellbore. The casing may be a casing section or, in the alternative, a casing string including two or more casing sections threadedly connected to one another. After the first casing is lowered to the first depth, cement is typically circulated into an annulus between the outer diameter of the first casing and the wall of the wellbore to set the first casing within the wellbore.
After setting the first casing within the wellbore, the drill string is re-inserted into the wellbore through a bore of the first casing and used to drill to a second depth within the earth formation. The drill string is again removed, and a second casing is lowered into the wellbore and set therein using cement. This process is repeated with additional casing until casing is installed within the wellbore to the desired depth.
While the casing is being lowered into the wellbore during the “casing running” operation, the pressure within the wellbore is typically higher than the pressure within the bore of the casing. This higher pressure within the wellbore exerts stress on the casing as it is being lowered into the wellbore, risking damage or collapse of the casing during run-in; thus, a casing fill-up operation is performed, where the bore of the casing being run into the wellbore is filled with a fluid (often termed “mud”) in an attempt to equalize the pressure inside the casing with the pressure outside the casing (the pressure within the wellbore) and thereby prevent collapse of the casing during the run-in operation. Pressurized fluid is typically input into the bore of the upper end of the casing using a fill line from the existing mud pumps at the well site.
At various times during running of the casing into the wellbore, the casing often sticks within the wellbore. To dislodge the casing from the wellbore, a circulating operation is performed, where pressurized drilling fluid is circulated down the casing and out into the annulus to wash sand or other debris which is causing the casing to stick out from the lower end of the casing. To force pressurized fluid out into the annulus for the circulating operation, a circulating tool is utilized.
To “rig up” the circulating tool for the circulating of fluid through the casing, the circulating tool is inserted into the bore of the casing at the upper end of the casing. A sealing member on the circulating tool is then activated to seal the circulating tool with the casing, forming a path for fluid flow through the circulating tool and out into the bore of the casing. Specifically, in a circulation operation, fluid is introduced into the circulating tool, flows through the bore of the casing and out the lower end of the casing to remove the obstructing debris, and then the fluid having the debris therein flows up the annulus to the surface of the wellbore.
After the circulation operation, the circulating tool is removed from the casing to allow another casing fill-up operation and further running of the casing into the wellbore to occur. During the casing running and fill-up operations, air must be allowed to escape through the bore of the casing to prevent over-pressurizing the bore of the casing. To permit the air being replaced by the fluid during the fill-up operation to escape from the bore of the casing, the circulating tool must be removed from the casing prior to the fill-up operation. To remove the circulating tool (“rig down”), the sealing member is de-activated, and the circulating tool is lifted from the bore of the casing. The casing may then be lowered further into the wellbore while filling the casing with fluid to prevent collapse of the casing.
Rigging up and rigging down the circulating tool, which are time-consuming procedures, must often be performed numerous times during a casing running operation. Therefore, attaching and re-attaching the circulating tool each time the casing is stuck within the wellbore during casing running is expensive and decreases the profitability of the well. Furthermore, because rig personnel perform the rigging up and rigging down of the circulating tool, which are often dangerous operations, numerous rigging up and rigging down operations decrease the safety of the well site.
Thus, there is a need for a method for circulating fluid for a circulating operation and filling up the casing with fluid for casing running and fill-up operations without the need to rig up and rig down the circulating tool every time a circulating operation must be performed. There is a further need for a circulating tool which is capable of performing both the fill-up and circulating operations without removal of the circulating tool from the casing. There is yet a further need for a circulating tool which allows air to escape while maintaining the circulating tool inside the casing during the duration of the casing running operation.